It is already an indelible image of Pope Francis’s first trip abroad: a giddy crowd of well-wishers swarming the pontiff’s car after it made a wrong turn in downtown Rio de Janeiro, overwhelming his meager security detail — and delighting the man in the back seat.

Francis waved at the raucous mob through open windows, and even kissed a baby that a woman handed him through his car’s open windows. The pope was transferred to an open vehicle where he finished the ride, beaming.

But it was classic Francis, who since his March election has insisted on an informal, populist approach to the papacy, with a special concern for the poor and downtrodden. “He is setting a standard for us all to imitate,” said the Rev. Roger Landry, a Diocese of Fall River priest.

In Rio on Thursday, Francis suggested to a group of Argentine youth that he wants young people to shake up the church.

“What do I expect as a consequence of the Youth Day? I expect a mess,” he said, according to the ZENIT Catholic news agency. “There will be a mess here in Rio? There will be! But I want a mess in the dioceses! I want people to go out! . . . I want us to defend ourselves against everything that is worldliness . . . that is comfortableness, that is clericalism, that is being shut-in in ourselves.”

On Friday, he addressed hundreds of thousands of youth on Copacabana Beach, where a cast of young people portrayed the Stations of the Cross as the problems facing youth, including violence, imprisonment, and illness. Invited to greet Francis on the main stage — at his request, the Vatican said — were about 35 Argentine landfill workers, or cartoneros.

“Sometimes, we can be like Pilate, who did not have the courage to go against the tide to save Jesus’ life,” the Pope said, according to an advance copy of his remarks, referring to the Roman authority who authorized the crucifixion of Jesus.

In Rome, Francis has shown no compunction about going against the tide. He has shaken up the Vatican bank and appointed an advisory council to help him reform the church bureaucracy. He did not show up to a classical music gala in Vatican City where he was to have been the guest of honor. But he found time to visit an island in southern Italy where asylum seekers and migrants pour in by boat from North Africa.

He lives in a modest two-room suite at Casa Santa Marta, a Vatican guest house, rather than the opulent Apostolic Palace. In simple homilies for the visitors and workers there at Mass each morning, he emphasizes doing good and caring for the poor. One day in May, he preached that even atheists can be redeemed, generating headlines around the world.

“We must meet one another doing good,” he said. “ ‘But I don’t believe, father, I am an atheist!’ But do good: We will meet one another there.”

He prefers open cars or, better yet, walking among the people, as he did this week in Varginha, a slum community so wracked by drug and gang violence that police were sent to occupy it last fall.

“His instinct — he’s done it again and again — is to be with the people,” said Kathleen Sprows Cummings, director of the Cushwa Center for the Study of American Catholicism at the University of Notre Dame.

The Rev. James Martin, a Jesuit author and contributing editor at America magazine, said he believes Francis’s papacy will be “a revolutionary one” because of his emphasis on the poor, his simple way of life, and his down-to-earth way of speaking about the faith.

“It doesn’t mean he is changing any of the essentials — he is still focused on Jesus Christ and proclaiming the gospel — but he is putting his own personal stamp on the office in a very dramatic way,” he said.

Francis, the first member of the Jesuit order to become pope, has dismayed some traditionalists who miss Pope Benedict XVI’s liturgical formality, and disappointed others who complain that the new pope has not emphasized the church’s moral teachings on abortion and same-sex relationships.

Vatican observers took note this week when Archbishop Charles Chaput of Philadelphia, who is in Rio with the pope, told the National Catholic Reporter’s John Allen that members of the church’s right wing “generally have not been really happy” with Francis and that the pope will have to find a way to “care for them, too.”

But the Rev. Mitch Pacwa, a host on the Eternal Word Television Network, said he has not heard many complaints. What he has noticed — as Chaput noted in that interview — is that people outside the church are paying attention to Francis.

Pacwa said he loves all three recent popes, but for those alienated from the church, “John Paul was difficult to understand because he was a philosopher. Benedict just didn’t connect with them, and he had a lot of bad press, they would call him the Rottweiler, he didn’t capture a lot of people’s imagination.

“But this guy does,” he said. “All the popes are against consumerism, but this guy brings the hay down to where the goats can get it. He told the priests, ‘I don’t want you driving fancy cars.’ ”

It is too soon, most scholars and Vatican observers agree, to assess whether Francis will effectively address the most serious problems facing the church, including alleged corruption and infighting within the Vatican bureaucracy; bishops who fail to enforce sexual abuse protocols; rising secularization in the West; and the tide of Pentacostalism that has diminished the Catholic Church in Latin America.

The Rev. Mark Massa, dean of Boston College’s School of Theology and Ministry, said he is waiting to see who Francis appoints to replace Cardinal Tarcisio Bertone, the Vatican secretary of state who resigned last month. “Then we’ll have some sense of what this papacy is going to be about,” he said. “Until then, I welcome the stylistic changes.”

There are signs, however, said Francine Cardman, a professor of theology and church history at Boston College, that Francis is taking steps toward substantive change. She said the pope, in a recent address to the Vatican ambassadors who make recommendations for local bishop appointments, said he wanted men who lived in poverty and demonstrated concern for the poor.

Martin said a friend going to stay at the Casa Santa Marta recently asked Martin to give him copies of several of his books so he could pass them along to Francis. Last week, Martin was stunned when he received a handwritten thank you note from the pope. The return address reads: “F. / Casa Santa Marta, Vatican City.”